Subject: Re: files/process scaling problem? (was: [PATCH] Export
	shmem_file_setup and shmem_getpage for DRM-GEM)
From: Keith Packard <keithp@keithp.com>
To: Ingo Oeser <ioe-lkml@rameria.de>
Cc: keithp@keithp.com, John Stoffel <john@stoffel.org>,
       Christoph Hellwig <hch@infradead.org>, Eric Anholt <eric@anholt.net>,
       linux-kernel@vger.kernel.org
In-Reply-To: <200808040135.32563.ioe-lkml@rameria.de>
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	 <18581.43362.460694.60862@stoffel.org>
	 <1217785943.23437.330.camel@koto.keithp.com>
	 <200808040135.32563.ioe-lkml@rameria.de>
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Date: Sun, 03 Aug 2008 17:19:12 -0700
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On Mon, 2008-08-04 at 01:35 +0200, Ingo Oeser wrote:

> What actions on many thousand fds are supported poorly or not at all?
> Are you only concerned about the memory requirements?

I didn't notice that the change in the maximum number of fds per process
from 1024 to 1024*1024 back in February. That makes it possible,
although requiring root privs, to allocate enough fds for this to work.

The other issue is that several important applications (including the X
server) use select instead of poll, and they have a small maximum number
of fds that they support. It seems like this could be worked around by
dup2'ing the shmem fds up a ways.

> Please elaborate or point me to a place where you did already :-)

I should have looked at fs/file.c.

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